1. Field of the Invention
The present invention relates to a charge control circuit, a charge circuit, and a mobile electronic device.
2. Description of the Related Art
Recent years, charging systems which perform charging via USB (Universal Serial Bus) interfaces are broadly adopted as those for mobile electronic devices including a secondary battery, such as a portable music player. For example, Japanese Laid-Open Patent Publication No. 2011-62022 discloses a charge circuit that converts electric power supplied from a power supply such as a USB power supply into electric power for charging a secondary battery such as a lithium-ion secondary battery using a DC-DC converter, and performs constant-current charging or constant-voltage charging.
By the way, an electronic device such as a digital video camera which requires higher power supply voltage may include two-cell lithium-ion secondary batteries (for example, full charge voltage of 8.4 volts). However, in the charge circuit of Japanese Laid-Open Patent Publication No. 2011-62022, the voltage (e.g., 8.4 volts) for charging two-cell lithium-ion secondary batteries cannot be generated from the USB power supply voltage of about 5 volts since a step-down DC-DC converter is employed.